**Description:**
Auth logout is not scoped correctly. Logging out from a local session terminates the global authentication instead of only clearing the local repository's credentials.

**Scenario:**
1. Terminal 1: Logged in globally via `ngit account login`
2. Terminal 2: Logged in locally within a git repo via `ngit login --local`
3. Terminal 2: Run `ngit account logout`

**Expected:**
Logout only affects the local repository session in Terminal 2. Global authentication in Terminal 1 remains active.

**Actual:**
Logging out in Terminal 2 also terminates the global account session. The global auth state is cleared unexpectedly.

**Impact:**
Users cannot manage local and global authentication independently. Re-login is required for both contexts after a local logout.

**Suggested fix:**
- Scope auth token storage to the appropriate level (global `~/.config/ngit/` vs local `./.git/ngit/`)
- Ensure `ngit account logout` respects the local/global flag and clears only the intended scope
- Add a status command (`ngit account status`) to show which scopes are authenticated